Data centers house servers that serve web content and/or route network traffic. Servers rely on electric power generated from power supplies that are typically stored in close proximity to the servers or in some cases inside the server chassis. Preferably, the power provided is reliable and regulated. In some cases, two power supplies may power a server or group of servers so that the servers have power even if a power supply fails. The power supplies may include a data bus interface to send and receive messages so that the power supplies can be managed. The power supplies may be managed to control the overall heat output of the data centers, for example. Improvements to managing the power supplies are desirable.